Thank you for your clear and informative videos. I am a commercial Heating / Plumbing Engineer and have some dealings with electricity but am keen to expand my knowledge and find your videos very good. Thank you for sharing your vast knowledge.
A very useful video, for work at Heathrow they actually specified which tester and proving unit must be used. I of course asked the question regarding using a multimeter. Your explanation was far better than theirs.
My favourite tester is the old solenoid tester I have, you don't need to see the thing, you can feel the 'hum' from it on AC, and it gives you a rough idea of voltage on the 'display' if you look at it, so you can tell the difference between 110, 240 and 415v supplies And good call on the people who will say they have had hundreds of shocks. It shows laxity if they have. The one you don't think will kill you is the one that will.
Thanks JW for an excellent video. I’d like to make a couple of points… The Drummond test lamp you demonstrate was my favourite but is obsolete now. The latest models (MTL-10 or 20) look the same but use a tower of very bright LEDs to indicate voltage. They now works on RCD circuits without tripping them when measuring live to earth. Still my favourite for its robustness and clear indication. It’s very important to test all combinations of connection, L-N, L-E and N-E. I’ve investigated an accident in which a test L-N showed no volts but the electrician still got a nasty shock. A “borrowed neutral” raised the whole installation to live potential, despite the fully functional double pole isolator being “off”. To those commenters still saying to use a multimeter - I back JW 100% in saying this is dangerous - there are numerous subtle ways they can mislead or fail. I have investigated incidents in which multi-meters and non-contact volt-sticks failed to indicate live circuits and accidents occurred. In the UK the Health and Safety Executive [HSE] publish a guide “GS38 Electrical test equipment for use on low voltage electrical systems”. The HSE also recommend “Guidance on the management of electrical safety and safe isolation procedures for low voltage installations” from Electrical Safety First. Neither of these useful guides recommend multi-meters or volt-sticks for proving dead.
As a mech eng this looks perfect. Really greatfull for all the safety guidance too. I am that guy who will poke around and probably have the wrong lead / switch setting. Many thanks
I was 4 years old, and my Dad has shown me the way how to test 1.5V batteries. As an inquisitive child, I have extrapolated that knowledge and licked the live and neutral wires. It didn't hurt: I lost consciousness for about 3 minutes. No cardiac issues, etc Now I'm just using the extensors side of my limbs to check 230V - still no issues!
Far better than licking in emergencies is touching the suspected item with the back of your fingers, with your fingers extended. The muscle contraction with any shock will pull your fingers, hand, and forearm away from contact. It is a useful technique for a quick check on steel enclosures, handles, etc. before opening them up. It's much more sensitive than a neon screwdriver.
@@johncosgrave9132 I believe firefighters use a similar principle using the back of their hands when feeling through the smoke, in case there are live cables.
The fundamental principal of electrical safety, is simplification, i.e. reduce the amount of possible failure paths. Use of a Multimeter to test for dead introduces the possibility of multiple failure paths as John explains in his video. However there is another aspect to testing that should be considered. The use of a combination of test instruments then reduces the possibility of a miss-test. I personally use a combination of both electronic and resistive test instruments when dead testing anything over 500v. It's just my own prerogative in the same way as I apply my own padlock on an isolation carried out by somebody else. Belt and braces.
A very interesting video. I use a Martindale tester, which was the approved device at work plus a proving unit. It's basic, fairly small, no frills but very reliable. Its capable for both AC and DC circuits. The proving unit is pocket sized so no excuse for not using it before and after a test. The voltage test screwdriver you showed doesn't work if you're wearing gloves and it's a candidate for the bin. We have access to Fluke multimeters which are not recognised as approved testers.
Another issue with using a multimeter to prove dead is that even if you have the setting correct (voltage, AC, right range etc) - you may still have the your test lead plugged into the current terminal 'A' and you will now be putting a short across your circuit! If the circuit is live then hopefully the internal fuse in the device pops quickly And in the test lead probes (if they comply with GS38!) Using 500mA fused test leads when measuring voltage is a good idea. ..regarding the screwdriver, they are helpful for confirming correct polarity at PME cutouts... a test lamp/similar device will light/give you the right voltage values, but the cutout could still be reverse polarity!.. the screwdriver test will show if voltage is present on the combined neutral-earth, or not. Testascope is a sinilar product that serves this purpose. Or when testing a plug socket with a Bicotest Tru-pole. Cheers
JW I'm up to 6 shocks, all could have been avoided. One shock was from a £5 tool fair multimeter where the leads had snapped under the insulation giving a false reading that the supply was de-energised.
Your demonstration did not in any way cover the possibility that neutral may be switched off but not the live wire. I only say this because you went into great detail about many unlikely issues, but this is actually a much more plausible problem which you completely failed to cover.
^ I have thought the same thing, I used to own a pair of digital testers like in the video and they will tell you if a dangerous voltage is on a conductor with only one probe touching, it didn't matter which one it was. It wouldn't tell you what the voltage was without a reference. Just out of interest one day i stuck one probe in a plug socket in the kitchen and the other on the steel casing of the dishwasher, 240v obviously. Take the probe off the dishwasher (one still in the socket) - red led (AC warning*beeping). One probe in socket and one in dry hand (boots on, tile floor) - nothing. One probe in socket, one in hand, bare feet, about 100v One probe in socket, wet finger on other probe and holding dishwasher, 240v. They are much more reliable than test lamps/proving units, which like you said might not prove anything if you don't prove it is live first
i had a active neutral supply reversal ..by the provider...did nasty things...was not happy when i found it...the provider was working in the street...they were seriously. embarrased.
260v is very high. I've never seen more than 250v. At my firm in the sticks, it sometimes gets as low as 200v much to the dismay of our governor. We are an electromagnetic Compliance company, on the low days we can only test to FCC and Japanese standards...
I can appreciate your approach but for me and the 45 years of experience I have working with electrical sources the only reliable method is the multi meter. I have seen way too many mis-wired mains and other supply boxes to in any way feel safe except by verifying it with a multi meter. I have also seen too many people take a shock because they only checked the terminals they expect voltage on. One time a tech actually cross wired 480 volts triple phase connecting the ground lead from the Control Van to one of the phases of 480 at the feed breaker. Let me tell you when he turned on the breaker it was quite the show. Never trust the color code, a person connected it, verify that the connections are according to code by testing it. Good quality multi meters and probes are rated for 600 VAC. When you need to measure higher voltages High Voltage Probes are used. I have regularly used this to check and test 3000 VAC circuits. The Multi Meter gives you the ability to make several different tests but it does require you to understand what you are doing. Any meter or test instrument can give you false or undefined readings if used improperly. I always told my guys to be smarter than the test equipment and tools they were using.
richb313 this definitely seemed like a home gamer oriented video. Every maintenance tech/engineer I’ve ever worked with in the field has used a non contact power indicator followed by a multimeter/wiggy after testing on a know live circuit. Coil wiggys are handy for those phantom voltages from long wire runs, sometimes digital meters are too sensitive and give a reading of voltage but no amps behind it. The proving unit looks handy.
If you don't understand the test instrument you're using you should'nt accept the result. DMMs have a high Z and can pick up radiated fields from surrounding wires. To this end, Fluke used to supply a high resistance parallel load to eliminate the ghosting. Most of the instruments shown are sufficient if you know understand the science. Unfortunately electricians are not engineers or electronics technicians.
A voltage tester wont work across L-N with a neutral fault either. L-E with both sorts of tester would indicate the presence of a voltage however in some circuit configurations. The argument against multimeters is the potential for incorrect setting but that isnt a very strong argument either in my opinion because we have to use MFTs to do all sorts of live test work that also requires us to set the instrument to the correct setting. This procedure John Ward talks about is really aimed at the keeping the incompetent professionals (we all know one or two of those) safe, those people who make mistakes. Even a complete idiot can use a single function 2 pole tester and a proving device after all, its an idiot proof test.
In a commercial situation the person doing thee job has to to a Risk Assessment. This would take into consideration things such as lack of external supply.
One question: The test you showed only seems to prove that at least live or neutral are disconnected (in case of a partial failure of the RCD). Should one therefore not test live against a known and still connected earth or neutral too?
+Shoppinguin It happened to me too. Since then I make sure to have a connected earth available (extension lead) whenever I do that. I only thought I had missed something.
A test sequence should be more like Do a proving test on the measuring device test: L in ~ N out test: L out ~ N in Do a proving test on the measuring device
I am an electrician by trade. Multimeters are the most reliable tool for verifying power. They also tell you what your voltage is so that you know that the power coming in is in the correct range. If you're worried about having to set ranges or accidently going to manual ranging, buy a multimeter that has no manual ranging function. If you are worried about having to change lead positions and possibly getting it wrong, buy a multimeter with hardwired leads. Your best bet in the long run is to learn how to properly use a multimeter. Hot sticks (proximity testers) are considered the next level of reliability but have low end detection ranges (usually 24 or 50 volts), but do not tell you how much power is on the line. I have seen hot sticks detect induced power on a line because the induced voltage is enough for the hot stick to detect. Voltage detectors that use indicator lights have the flaw that you can blow out the lamp by over voltage, and that under voltage gives you a no power indication. If you want to be absolutely sure that you have no power, your most reliable choice is the multimeter. Of course, with all these pieces of equipment you should always verify proper working condition before usage, which includes checking operation on a known live power source within the operating range of the tester. Be aware of the category rating of your meter when you purchase it. It is part of the safety rating of the test equipment and has to do with how much protection is between you and the unprotected power source (power lines). faculty.riohondo.edu/jfrala/fluke_multimeters_-_abcs_of_multimeter_safety_multimeter_safety_and_you_application_note.pdf
***** That doesn't eliminate the fact that a good multimeter is by far your most reliable test device for power. However, the rule of thumb that anyone who works regularly with electricity is that when working around live circuits, treat the wires as if they have power on them even when you have verified that the power is off. If you were to have a combination of tools to verify power, both proximity tester and multimeter should be used in tandem for power verification.
+Ian Belletti i prefer voltage/continuity testers. They usually have a higher safety class and most of them have single pole indication where as a multimeter often doesn't.
FoodOnCrack The multimeters I use do both voltage and continuity tests. The rating of the meter as far as voltage range and category location are what give you the safety of the meter when it comes to available fault current. Your safety as far as verifying power comes in knowing how to properly use your tools. Proximity testers handle your single pole situations when the return path is broken, however, multimeters are still undefeated as far as power verification ability. Both have their shortcomings, but using both multimeter and proximity tester will give you the best warning as to the possibility of shock on the circuit. Of course it's recommended that you verify that your test equipment is working on a known live circuit prior to testing the circuit in question, especially the proximity tester.
that is why i prefer voltage/continuity testers. They have single pole indication, so it basically is the same as a neon screwdriver; you don't need neutral or ground for it to light up.
Good video JW. Keep em coming... There are only 2 recommended instruments to prove Not Live. One is the Drummond test lamp, with a double filament bulb, we've all heard the story about the single filament bulb. (ALWAYS TEST BEFORE AND AFTER with a proving unit). The other is a contact volt probe/tester, as opposed to a non-contact. Use both, ALWAYS!!! Locking off and posting warning notices is another story...
Maybe. I use multimeter and for all the rare cases I short circuit the wires so they abosutely are not live. I can't recommend it thou. Don't fall from the ladders when doing that.
def ender I have used one of those screwdrivers once or twice when desperate, but always checked it's working with the power on first. Still I don't trust them and have always used my multimeter. Never had a problem as I always Che know my settings before using. Kinda pilots check list mentality - leads in correct sockets - check, a/c range - set and again check it's working on live before checking to see its off.
John, pleased to see you discussed the use of a proving unit but it would have been helpful to mention that any test meter/indicators should be GS38 compliant - meaning that the test leads should be fused. I wonder who you aim your video's at because any qualified and suitably trained person would know how to use a Multimeter and know whether they had it on the correct setting or not.
Mr Ward, I’m very much enjoying your informational videos. They are the perfect companion to the City & Guilds courses. I have a question for you regarding safe isolation. In your video here, and in the labs at the college they only ever show safe isolation of the complete system i.e. testing at the load side of the isolator to ensure all circuits in the consumer unit are dead. Are you able to show how you would isolate an individual circuit, for example the lighting circuit, whilst leaving the other circuits live?
After doing some DIY work over the years including 3 phase, one extra safety tip I do after checking the power is definitely off, is touch the wire with the back of your fingers. That way, if the wires were still live and all the muscles in your arm and hand contract, your arm/fingers will be pulled away from the live wires, instead of gripping it harder if you had used the inside of you hand.
But what if neutral wire is accidentaly disconnected or corroded away?? Two lead testers will not indicate voltage on live wire. Neon screwdriver is the only tester that will be able to indicate dangerous voltage in such case! It's the only one tester that really indicates if current will be going through your body if you touch the wire. It's quite reliable if you test it before and after use and if you learn to watch the lamp carefuly. However if the small resistor inside gets shorted, you will get nasty shock.
Can I just add you need to test not just L-N but L-E and N-E as a faulty switch or RCD may break the circuit N but leave the L connected. Also 264v is above the maximum supply voltage you should be getting ESQCR specifies 230v +10% / -6% so 216v to 253v.
There is a little flow in your presentation: let's pose for the moment that the neutral wire is broken. Will those fancy testers show that the power is on the live wire? What will happen if you 'reverse the polarity' and touch your Fluke main probe to the ground and the auxiliary probe to the live pin? Just curious.
The one probe indication is a secondary feature, similar to those 'volt sticks' with the red LED in the end. Both probes should be used, and that is the only way to get a display of the actual voltage.
It is useful in that it shows instantly of a potential lack of live or Neutral but just as a neon screwdriver is not a trustworthy tool, the proper checks need to be made. People still don't get it do they !
John I noticed that your Fluke was reading 263 volts. I have been left the UK now for 12 years but before I left the voltage was 240 volts. Then the decision was made to make the UK the same as the EU continent at 230 volts. There was a tolerance though of I believe 6% so it allowed the UK to still operate at 240 because it was covered in range by that 6%. But 263 is out of that range isn't it?
263 is far too high, the limit is 253 (+10%). The test setup in the video was supplied from an isolating transformer, which has a higher than normal output voltage with no load connected.
I have an Di-Log DL114 auto ranging MM with a red light which is detects current on non contact basis or if one of the probes makes contact to a live conductor. It has a built in torch too. £28
John - could you do a video on DIN rail terminal blocks? I'm aware that there are types that 'bus' together and others that are electrically isolated. Thanks
Good video JW, I have a cheap multimeter here (a present someone got me, I would never buy cheap multimeters myself) thats going spare I can send you so you can blow it up when you do your video on CAT ratings. I have all fluke meters anyway so it wouldnt be a loss.
When testing at a socket for example. You should get 240v between live-neutral and live and earth. However should you get continuity between earth and neutral. And also when testing dead, should you get continuity between live and neutral, if appliances are still plugged in, but no continuity between earth and neutral?
In the Netherlands appliances for proving 'dead' mains have to comply with NEN-EN-IEC 61243-3 or equal ( According to NEN 3140: 2015 6.2.3.101 ). A multimeter is not produced according to this standard and is therefor not suitable to use it that way. The procedure for proving 'dead mains ( 3 fase and neutral and PE )is as follows: -Be sure the tester works -test L1-PE , L2-PE,L3-PE,N-PE L1-N, L2-N,L3-N, L1--L2 ,L1-L3 ,L2-L3 and finally the last test for assuring the tester is still in working order. for a 230V it would go as follows -Be sure the tester works test L-PE, N-PE,L-N and finally the last test for assuring the tester is still in working order. I wonder if there are different sets of rules for proving dead mains between countries?
When I was an apprentice, they told me "To prove him dead, you must cut off his head". That was some time before I changed careers and got into the electrics.
I have a chinese version of the multifunction voltage tester (UNI-T UT15) and it has an on-time limit of 30 seconds followed by a rest period of 10 minutes, presumably due to power dissipation in the input part of the device that covers the wide range of 12V to 690V. I wonder if the Fluke voltage tester you showed also has that test period limitation?
...aaand even *AFTER* all that excellent advice, if your're going to work on two bare wires for a ceiling fixture, touch both conductors together with one hand BEFORE reaching with the other. If you have done what is aptly described here, it should be a simple final check before potentially sending a deadly current through your heart. Worst case scenario, you burn a hole in one hand instead, while you scratch your head with the other, wondering how the hell did that happen.
Hi.can you explain a 3phase and neutral supply how is there not 3 neutral supplies when there is 3 100 A fuses I thought if 50A goes along the phase cable 50 A comes back through the neutral which would put 150A through the 1 neutral overload it I am talking about using the 3 fuses for 240 v systems can you tell me how this works and does not overload the 1 neutral. Cheers
If only one phase is loaded, neutral current will be the same as that phase. If more than one phase is loaded the neutral current will be less, and if all 3 have the same load connected neutral current is zero. The three phases are not the same, each is phase shifted by 120 degrees, so that when one is at the peak AC voltage, one of the others will be at zero. Current flows from one phase to another, and the neutral just handles any imbalance. More extensive description here: en.wikipedia.org/wiki/Three-phase_electric_power
I was nearly killed once when I trusted a volt stick so I can confirm they are not suitable (I tested it on a known live wire and it lit up, tried it on one I thought I had disconnected - tried it several times) then cut the wire resulting in no more wire cutters ! Just wondering - if the RCD had developed a fault or was wired wrong and it was only switching the blue wire wouldn't the suggested technique in your video give a false safe indication?
I get concerned by the number of people saying, "i have had lots of shocks and feel fine", "or 240v or 110v doesn't hurt that much, stop being a wuss" what is all the fuss about?" ect, They completely miss the point, it only takes their body resistance to be low enough to cause a fatal shock, which is only milliamps, why do you think an rcd is designed to trip as low as 30ma? The mains supply in your house is more than enough to kill you, whether its 240v in the uk, or 110v in america, they are both enough to kill, your body resistance determines the shock level of it being a slight tickle or nip to meeting your maker (in other words DEAD!!!) Electrocuted! and of course as you say john we won't be hearing from them.
That closing statement I believe has to with something called “Survivorship Bias” Where you only look at the survivors and ignore failure And then use that to be overly optimistic towards something Or in this case: be overly lax towards safety
And when the supply is off- make sure it is under your control! About 45 years ago i was examining a long extension lead that had failed- A man walked past the plug and an reasoned that the reason for failure was that it was not plugged in- so he did that- he then ran outside to investigate the screaming..... I was me connected - the man was my brother........... I often wonder.
John, I tend not to use any of this equipment when I’m testing my circuits; instead I do prefer to get my little brother to touch the wire I’m unsure about. It’s simple if he doesn’t get a shock I know the circuit is dead, if he gets thrown across the room it means the circuit is live! Easy!
I haven't used it, but it is made by a known test equipment manufacturer (Mastech), Screwfix have just had it relabelled for their own use. It's very basic but should be OK for voltage indication.
Your Video is done perfectly by the Book. Sadly the Book does not cover everything. it is also slow to adopt new stuff coming up which in my opinion makes much sense. In no particular order: 1. You didnt mentoin that the most common tester can also detect/show dangerous Voltages with only one wire connected. you can briefly see it at 9:05 before you connect the N that the AC lamp briefly lights up alone. If this happens with both leads connected but its not showing a Voltage you should double and triple check because something is probably very wrong then.. (and the first tester you showed would very likely have shown something in that case) - yes such things happen. A Co-Worker once told me about such a situation where a Cable was cut inside a Wall with a Wall Chaser but only N and PE got cut, L was still connected - he was glad he had one of the Screwdriver type Tester at hand because the other testers he used before didnt show anything (this was probably 20 years ago so they were older ones without that feature) 2. You said tha the Test Leads must be insulated that at most 4mm of it is uninsulated. While i agree with the general thought in practice these kinds of probes are simply not useable because you cannot get the probe to contact properly in the most commonly used Connectors today (we use the Wago 221, and back when this video was made the previous generation which had the same problem), and it would be very wrong to assume that the wiring box is Voltage free if you cannot get proper contact with the wiring. I usually cut the Insulation a bit to mediate this - barely enough that i can click my Probe into a Connector of aforementoined Wago 221 (thats about 6 or 7mm exposed metal on the probe - this is also perfect for using the Test contacts on these Connectors.) The 4mm Rule certainly made sense back when these Screw Things were commonly used, but i am glad we screwed them.. 3. While the Screwdriver-type Neon Testers are certainly not a good choice as Voltage Tester i like them for another purpose: they are perfect to unlock the Spring-type Terminals in Distributors, and also to Slide the N Disconnector. Or when you happen to come across a Screw Connector. Its pretty difficult to find appopriate Screwdrivers in the right Size as single Item (i dont need it included in a set of other Scredrivers, as usually only the small ones break). I personally would favour a Combination of a small Screwdriver and a Test Lead (basically a Screwdriver with a Ø4mm Socket for the test lead), but so far i had no success finding one.. As additional Measure: if you work with many Circuits and the way from the Distributor to the Working site is pretty long: there are also these new Fuse Finders which add an additional check. Plug them in on the desired Circuit, check for their Signal in the Distributor, Switch off Circuit and the Signal should disappear almost instantly (if it doesnt something is wrong). After that check again with one of the allowed Testers of course. When switching on do it the other way: plug in Transmitter on the Circuit you want to switch on, hold Receiver close to the Fuse and when switching it on you should quickly get a Signal. If not something is wrong and you should quickly switch the fuse off again and re-check your stuff. Certainy not a Requirement, but if you work with many Circuits it makes much sense in my opinion (better than leaving an unknown cable live while you go to check the Socket or whatever you are working on and walk back to switch it off if it doesnt check out).
Hello John! I like electricity, especially transformers, 3 phase motors, but also I like to work with circuits. My question is : What type of multimeter can you recommand me? I am looking for a Fluke T-130, but I also like Fluke 113 and 114. Now I have a PeakTech 3340 which is working ok.
When using voltage probe testers, does it matter which terminal you put the needle in. If so, what terminals does the positive and negative go into? What would happen if you did it the wrong way? And also if I wanted to test a socket through the pins, where would I put the needles?
When you use that neon test driver, is it interfering with your microphone where you become part of the circuit? every time you touch it to the circuit, I can hear a faint buzz.
A proving unit is still required, as it's necessary to create the 400+ volts to prove it with. Some have a built in function to test, but that's only for confirming the indicators on the device are working, that can't replace testing it on an actual 400+ volt supply.
This info would be handy for working on automobiles, I think. Also, a topic suggestion for a future video. Why does the US (where I live) only use 120 volts when apparently everywhere else uses 240 volts? I do hope you eventually cover something like this. Would be interesting to see.
+Bryan Young That's quite interesting. A mate told me his take on it, and that is, Americans were first to receive electricity and it came in the form of 110 volts. Since then other countries had got it and realised that the 230 - 240 volt system was a heap better (more power I suppose) however Americans already had the 110 volt too well established into their infrastructure that it wouldn't be viable changing! A theory that would need proven, however, no doubt interesting all the same!
From what I understand, we have 240 pumped into our houses, though it gets chopped into 120 somewhere along the lines. Like our stoves, washers and dryers all use 240, of course with a different plug so you can't screw it up and plug in a nightlight there.
+Bryan Young You are getting 220V/60 Hz phase to phase with a neutral in the middle providing two 110V/60Hz circuits (two phase 180 degree system). Most of the world gets 3 phases with 380V/50Hz phase to phase and a neutral at the star point providing 3 x 220V/50 Hz circuits. Britain and its colonies used to get 415V/50Hz and 3x240V/50Hz. So before brexit, the EU compromise was to label it all as 400V/50Hz and 3x230V/50Hz. Not sure if that will be rolled back after Brexit.
Hi JW Can you please explain what happens at the pole transformer at the centre tap. I have ideas but need professional help with this one. I am a 69 years old student of the "Works of Nikola Tesla". .... Regards ..... DC
That's quite interesting! Thank you for explaining so much. I'm curious why the sound jumps sometimes when you touch the wire with the probing rods. Can you explain what's happening? This is not meant as a criticism I really want to know what's causing this, because I want to learn more about keeping audio clean my own work. It just seems weird to me that doing this can affect the sound of your camera because there should be no connection between the things, right?
Michael Hübner It will be capacitive / inductive effects, mostly being coupled into the wire for the microphone. Constant interference will be capacitive, and when connecting/disconnecting the probes inductive, as a small spark will be created at the probes - a similar effect when turning a switch on and off.
Real story - I was working in Hong Kong once and while wondering the streets taking in the sites came across a street stall which among other things was selling a fairly respectable looking neon screw drivers. I also noticed it had "made in West Germany" stamped on it. Oddly I could also see inside the open door of the factory and the people making the neon screwdriver. Perhaps there is a section of Kowloon known as West Germany. That was around 20 years ago but perhaps only the location has changed today.
KingOfKYA Yes, it's an isolation transformer. Otherwise it would not be possible to trip the RCD on the test stand without also tripping the rest of the circuit.
***** Ah right that true or you wold be poping the main rcd breaker. Another potentially interesting topic would be safety procedures when you have to work on live circuits, and possibly thouse with multiple power feeds.( datacenters hospitals etc)
hi john, what do you think of the various test leads that have a self test (working ) function built in ? ( ie. push a button th check if function is ok )
I have one issue with two test prong units. In case of faulty neutral connection most of test units don't notify about potential of getting shocked. My coleg once got pretty nasty shock testing with a multimeter( somebody has pulled the neutral wire from the junction box).I always test with cheap screwdriver type indicator. And its easier to carry it around than a two prong unit. I never had faulty indicator but i still test it on known live circuit before i use it to diagnose something. It has it's fault with the fact that it is hard to see the light shining in lit condition especially in daylight. Most indicators brake quite easily especially if you use thame as a screwdriver. And I believe there are conditions that it could not light up on live circuit (like on DC) but I didnt enquterd it yet in my work. P.S. In case of faulty neutral it quite easy to test it just by connecting some load on circuit and checking if indicator lights up on neutral terminal.
Actually fluke 117 has a great feature for proving dead, which is the auto low impedance volts range, definitely one of my favourite multimeters out there
Hi, I am a trained 'Authorised person' and would like to point out an error in the proving for dead procedure described above (around 11:00 onwards). The correct procedure for proving dead is a five stage (not three stage) procedure: Step 1 - Prove your tester (check it is working) Step 2 - Test Phase to Neutral (repeat for all three phases in a three phase installation) Step 3 - Test Phase to Earth (again repeat for all phases) Step 4 - Test Neutral to Earth. Step 5 - Prove your tested again (Check it is still working). Without steps 3 and 4, the neutral or even earth could be live and you would not be aware as the neutral and live are at the same potential (i.e. both at 240v or both dead, but with a live earth). Also, for the electricians using mulitmeters to prove dead (I used to do this myself!), I would like to point out that the real danger with this is the possibility of the 'multi' meter accidentally being in current measuring mode. (Anyone who says they have never tried to measure volts in current mode is either superhuman or lying). In most cases, this will just lead to a blown fuse and some embarrassment. In the worst case, you might believe the circuit is dead (though steps 1 and 5 above should contradict this) or worse, draw an arc with a risk of flashover and burns (it has happened). Work safely folks.
I MUST SAY I HAVE NEVER HAD ANY TROUBLE WHILE USING MY DURITE 0-798-50 CAT 2 TESTED IT AGAINST MY OLD AVO7 RESULTS OF WHICH ARE VERY VERY CLOSE I GET ON VERY WELL WITH EITHER OF THEM
I love John's videos, but this one I find lacking. For example, in case of neutral which gets to live potential (non that rare, due to shared neutral issues for example - and that can happen even in the middle of the work, not just at start!), in this video *ONLY* the Fluke (not main LEDs, but aux LED at top right) and "dreaded neon screwdriver" will actually work safely without endangering your life! Over here proper procedure for preparation of work on electrical installation was: (1) on the live output of main switch (input limiter/main breaker/main RCD) and neutral, check the instrument is working properly and input neutral is not broken (like main LED on Fluke or voltmeter or lamp test in this video) . (2) Turn off the breaker and check that neither the live nor neutral are at above-ground potential (NOT just the lamp/multimetar test, which wouldn't show broken neutral or neutral at 220V! Only Fluke aux AC LED shown at 8:43 and neon screwdriver from this video work for this!) (3) check on the input of main switch instrument is still working. (4) doublecheck with instrument that output of main breaker is really off. (5) short-circuit output of (now turned off) main switch live and neutral with your marked patch wire which you were carrying always with instruments/tools. (6) post a notice of "hazardous environment, warning not to touch the breakers, date and time of start of work and contact phone number" over the panel with patch wire and main switch. (7) proceed to work on the installation. This had a number of *additional* safety advantages to methods presented here, including: deterring people who wanted power and went to turn breaker back on while work was in progress (6), covering broken neutral (1), covering neutral at live potential (2), doublechecking (as just one check may not have made contact correctly) there is no live after input (2,4), making sure that even if live were to be introduced in any way while work is in progress, it would case dead-short and disconnect upstream instead of risking life of personnel (5). Of course there were also reverse procedure before turning power on (most importantly undoing 5, checking it is undone, and checking live/neutral before turning back on)
what happens if you put the probes the wrong way around? so in the video you were putting the black com cable probe onto the neutral & the red on live to get 261, but what if you did not know which cable was which or a cowboy job meant that you actually put the black com onto live & the red onto neutral... what would happen then?
I dont really understand all the hating on the regular multimeter :/ "If you dont know how to set this up, it wont read correctly" I'd say that if you dont know how to set up a multimeter, you'll need to learn how to, and not fall back to a possibly dead lamp.
In Germany it's mandatory to test your voltage tester on a functional circuit before using it. And I prefer the 2-pole voltage testers with a neon indicator in one handle and a plunger coil instrument in the other one. The neon indicator is for high impedance testing, and if you press a button you can switch over to low impedance testing. The plunger coil is indicating the voltage. Needs no batteries, and the lifetime of the neon indicator is much higher as the one of a standard lamp. But you won't get neon indicators showing the polarity on a DC-voltage anymore. Now they're using LEDs instead: abload.de/img/img_0123gesjq.jpg
The problem is that if you use multimeter for this application, one day you will be in the hurry, or simply be distracted, or meter will be malfunctioning, and you will put it in wrong settings or something or read incorrectly. It is not a matter of if, but when.
Yup, something like the "HOLD"-function. And multimeters have a high internal resistance. That's good for measuring inside of electronics, but not in a mains voltage circuit (reactive voltage). And the next thing is, with a multimeter you must turn away your view from the measuring point. And if working on a ladder a multimeter is very uncomfortable to work with.
I love the deadpan delivery, could listen to you all day!
Thank you for your clear and informative videos. I am a commercial Heating / Plumbing Engineer and have some dealings with electricity but am keen to expand my knowledge and find your videos very good. Thank you for sharing your vast knowledge.
Thanks for being here. Incredibly useful videos. Glad I found you. Cheers!
Love your closing speech John, brilliant,
Gotta love John's quality dry sense of humour!
Me too love it
You probably just saved me from wasting money, but more importantly, saved my life!
Excellent, very concise video. Thanks John.
A very useful video, for work at Heathrow they actually specified which tester and proving unit must be used. I of course asked the question regarding using a multimeter. Your explanation was far better than theirs.
My favourite tester is the old solenoid tester I have, you don't need to see the thing, you can feel the 'hum' from it on AC, and it gives you a rough idea of voltage on the 'display' if you look at it, so you can tell the difference between 110, 240 and 415v supplies
And good call on the people who will say they have had hundreds of shocks. It shows laxity if they have. The one you don't think will kill you is the one that will.
I still have my old solenoid style tester somewhere :)
Thanks JW for an excellent video. I’d like to make a couple of points…
The Drummond test lamp you demonstrate was my favourite but is obsolete now. The latest models (MTL-10 or 20) look the same but use a tower of very bright LEDs to indicate voltage. They now works on RCD circuits without tripping them when measuring live to earth. Still my favourite for its robustness and clear indication.
It’s very important to test all combinations of connection, L-N, L-E and N-E. I’ve investigated an accident in which a test L-N showed no volts but the electrician still got a nasty shock. A “borrowed neutral” raised the whole installation to live potential, despite the fully functional double pole isolator being “off”.
To those commenters still saying to use a multimeter - I back JW 100% in saying this is dangerous - there are numerous subtle ways they can mislead or fail. I have investigated incidents in which multi-meters and non-contact volt-sticks failed to indicate live circuits and accidents occurred. In the UK the Health and Safety Executive [HSE] publish a guide “GS38 Electrical test equipment for use on low voltage electrical systems”. The HSE also recommend “Guidance on the management of electrical safety and safe isolation procedures for low voltage installations” from Electrical Safety First. Neither of these useful guides recommend multi-meters or volt-sticks for proving dead.
As a mech eng this looks perfect. Really greatfull for all the safety guidance too. I am that guy who will poke around and probably have the wrong lead / switch setting. Many thanks
also always prove its dead yourself, never ever take someone's word for it, no matter how much you thrust them!
You didn't mention licking the live wire to check for voltage. Is that not standard practice?
Pissing on it is better. You feel it more.
I was 4 years old, and my Dad has shown me the way how to test 1.5V batteries. As an inquisitive child, I have extrapolated that knowledge and licked the live and neutral wires. It didn't hurt: I lost consciousness for about 3 minutes. No cardiac issues, etc Now I'm just using the extensors side of my limbs to check 230V - still no issues!
@@mernok2001 Megkérdezem a Szent Pétertől.
Far better than licking in emergencies is touching the suspected item with the back of your fingers, with your fingers extended. The muscle contraction with any shock will pull your fingers, hand, and forearm away from contact. It is a useful technique for a quick check on steel enclosures, handles, etc. before opening them up. It's much more sensitive than a neon screwdriver.
@@johncosgrave9132 I believe firefighters use a similar principle using the back of their hands when feeling through the smoke, in case there are live cables.
Great videos but lets cut to the chase here....when you going to play us a tune on the organ?
Classic !! :)
The fundamental principal of electrical safety, is simplification, i.e. reduce the amount of possible failure paths. Use of a Multimeter to test for dead introduces the possibility of multiple failure paths as John explains in his video. However there is another aspect to testing that should be considered. The use of a combination of test instruments then reduces the possibility of a miss-test. I personally use a combination of both electronic and resistive test instruments when dead testing anything over 500v. It's just my own prerogative in the same way as I apply my own padlock on an isolation carried out by somebody else. Belt and braces.
A very interesting video. I use a Martindale tester, which was the approved device at work plus a proving unit. It's basic, fairly small, no frills but very reliable. Its capable for both AC and DC circuits. The proving unit is pocket sized so no excuse for not using it before and after a test. The voltage test screwdriver you showed doesn't work if you're wearing gloves and it's a candidate for the bin. We have access to Fluke multimeters which are not recognised as approved testers.
Another issue with using a multimeter to prove dead is that even if you have the setting correct (voltage, AC, right range etc) - you may still have the your test lead plugged into the current terminal 'A' and you will now be putting a short across your circuit! If the circuit is live then hopefully the internal fuse in the device pops quickly And in the test lead probes (if they comply with GS38!) Using 500mA fused test leads when measuring voltage is a good idea.
..regarding the screwdriver, they are helpful for confirming correct polarity at PME cutouts... a test lamp/similar device will light/give you the right voltage values, but the cutout could still be reverse polarity!.. the screwdriver test will show if voltage is present on the combined neutral-earth, or not. Testascope is a sinilar product that serves this purpose. Or when testing a plug socket with a Bicotest Tru-pole.
Cheers
JW I'm up to 6 shocks, all could have been avoided. One shock was from a £5 tool fair multimeter where the leads had snapped under the insulation giving a false reading that the supply was de-energised.
and there we have it :-)
I am sure the electricians have their personal methods to test live/dead but your video is great for the DIY among us. Nice one.
Your demonstration did not in any way cover the possibility that neutral may be switched off but not the live wire.
I only say this because you went into great detail about many unlikely issues, but this is actually a much more plausible problem which you completely failed to cover.
^ I have thought the same thing, I used to own a pair of digital testers like in the video and they will tell you if a dangerous voltage is on a conductor with only one probe touching, it didn't matter which one it was. It wouldn't tell you what the voltage was without a reference. Just out of interest one day i stuck one probe in a plug socket in the kitchen and the other on the steel casing of the dishwasher, 240v obviously. Take the probe off the dishwasher (one still in the socket) - red led (AC warning*beeping).
One probe in socket and one in dry hand (boots on, tile floor) - nothing.
One probe in socket, one in hand, bare feet, about 100v
One probe in socket, wet finger on other probe and holding dishwasher, 240v. They are much more reliable than test lamps/proving units, which like you said might not prove anything if you don't prove it is live first
Yes, your preferred test methods only work if there is no neutral fault. This can be a significant risk in cowboy installations.
i had a active neutral supply reversal ..by the provider...did nasty things...was not happy when i found it...the provider was working in the street...they were seriously. embarrased.
260v is quite high. We get 240 maximum where we are.
Shaun Dobbie
That's England for you. Certain (cheap/dumb) electronics have funky behavior as a result of this (stronger vacuums etc).
Depends how near you are to the sub station.
I get 245-250VAC here most of the time
260v is very high. I've never seen more than 250v. At my firm in the sticks, it sometimes gets as low as 200v much to the dismay of our governor. We are an electromagnetic Compliance company, on the low days we can only test to FCC and Japanese standards...
17:00 You'll be hearing from their grieving widows John!
Excellent advice and presentation, thank you. That Hammond looks in good order, are you a musician?
I can appreciate your approach but for me and the 45 years of experience I have working with electrical sources the only reliable method is the multi meter. I have seen way too many mis-wired mains and other supply boxes to in any way feel safe except by verifying it with a multi meter. I have also seen too many people take a shock because they only checked the terminals they expect voltage on.
One time a tech actually cross wired 480 volts triple phase connecting the ground lead from the Control Van to one of the phases of 480 at the feed breaker. Let me tell you when he turned on the breaker it was quite the show. Never trust the color code, a person connected it, verify that the connections are according to code by testing it.
Good quality multi meters and probes are rated for 600 VAC. When you need to measure higher voltages High Voltage Probes are used. I have regularly used this to check and test 3000 VAC circuits.
The Multi Meter gives you the ability to make several different tests but it does require you to understand what you are doing. Any meter or test instrument can give you false or undefined readings if used improperly. I always told my guys to be smarter than the test equipment and tools they were using.
You are talking about fault finding which is not the same thing.
The two pole testers can also do continuity/resistive checks.
Proving dead should never be carried out with a multimeter, if in any doubt ask the HSE!
richb313 this definitely seemed like a home gamer oriented video. Every maintenance tech/engineer I’ve ever worked with in the field has used a non contact power indicator followed by a multimeter/wiggy after testing on a know live circuit. Coil wiggys are handy for those phantom voltages from long wire runs, sometimes digital meters are too sensitive and give a reading of voltage but no amps behind it. The proving unit looks handy.
If you don't understand the test instrument you're using you should'nt accept the result. DMMs have a high Z and can pick up radiated fields from surrounding wires. To this end, Fluke used to supply a high resistance parallel load to eliminate the ghosting. Most of the instruments shown are sufficient if you know understand the science. Unfortunately electricians are not engineers or electronics technicians.
A voltage tester wont work across L-N with a neutral fault either. L-E with both sorts of tester would indicate the presence of a voltage however in some circuit configurations. The argument against multimeters is the potential for incorrect setting but that isnt a very strong argument either in my opinion because we have to use MFTs to do all sorts of live test work that also requires us to set the instrument to the correct setting.
This procedure John Ward talks about is really aimed at the keeping the incompetent professionals (we all know one or two of those) safe, those people who make mistakes. Even a complete idiot can use a single function 2 pole tester and a proving device after all, its an idiot proof test.
What about considering the situations that external power has failed, giving false-positives on apparently disconnected power supplies?
In a commercial situation the person doing thee job has to to a Risk Assessment. This would take into consideration things such as lack of external supply.
One question:
The test you showed only seems to prove that at least live or neutral are disconnected (in case of a partial failure of the RCD).
Should one therefore not test live against a known and still connected earth or neutral too?
+Shoppinguin It happened to me too. Since then I make sure to have a connected earth available (extension lead) whenever I do that. I only thought I had missed something.
A test sequence should be more like
Do a proving test on the measuring device
test: L in ~ N out
test: L out ~ N in
Do a proving test on the measuring device
I am an electrician by trade. Multimeters are the most reliable tool for verifying power. They also tell you what your voltage is so that you know that the power coming in is in the correct range. If you're worried about having to set ranges or accidently going to manual ranging, buy a multimeter that has no manual ranging function. If you are worried about having to change lead positions and possibly getting it wrong, buy a multimeter with hardwired leads. Your best bet in the long run is to learn how to properly use a multimeter. Hot sticks (proximity testers) are considered the next level of reliability but have low end detection ranges (usually 24 or 50 volts), but do not tell you how much power is on the line. I have seen hot sticks detect induced power on a line because the induced voltage is enough for the hot stick to detect. Voltage detectors that use indicator lights have the flaw that you can blow out the lamp by over voltage, and that under voltage gives you a no power indication. If you want to be absolutely sure that you have no power, your most reliable choice is the multimeter. Of course, with all these pieces of equipment you should always verify proper working condition before usage, which includes checking operation on a known live power source within the operating range of the tester. Be aware of the category rating of your meter when you purchase it. It is part of the safety rating of the test equipment and has to do with how much protection is between you and the unprotected power source (power lines).
faculty.riohondo.edu/jfrala/fluke_multimeters_-_abcs_of_multimeter_safety_multimeter_safety_and_you_application_note.pdf
***** That doesn't eliminate the fact that a good multimeter is by far your most reliable test device for power. However, the rule of thumb that anyone who works regularly with electricity is that when working around live circuits, treat the wires as if they have power on them even when you have verified that the power is off. If you were to have a combination of tools to verify power, both proximity tester and multimeter should be used in tandem for power verification.
+Ian Belletti i prefer voltage/continuity testers. They usually have a higher safety class and most of them have single pole indication where as a multimeter often doesn't.
FoodOnCrack The multimeters I use do both voltage and continuity tests. The rating of the meter as far as voltage range and category location are what give you the safety of the meter when it comes to available fault current. Your safety as far as verifying power comes in knowing how to properly use your tools. Proximity testers handle your single pole situations when the return path is broken, however, multimeters are still undefeated as far as power verification ability. Both have their shortcomings, but using both multimeter and proximity tester will give you the best warning as to the possibility of shock on the circuit. Of course it's recommended that you verify that your test equipment is working on a known live circuit prior to testing the circuit in question, especially the proximity tester.
that is why i prefer voltage/continuity testers. They have single pole indication, so it basically is the same as a neon screwdriver; you don't need neutral or ground for it to light up.
Good video JW. Keep em coming...
There are only 2 recommended instruments to prove Not Live. One is the Drummond test lamp, with a double filament bulb, we've all heard the story about the single filament bulb. (ALWAYS TEST BEFORE AND AFTER with a proving unit). The other is a contact volt probe/tester, as opposed to a non-contact. Use both, ALWAYS!!! Locking off and posting warning notices is another story...
Fair play john, dry as a crisp ,love the humour as much has the video's, brilliant 😂😂😂😂
Point perfectly made with a bit of black humour at the end, love it.
Thanks very much for the critical safety tips J.W.
Very good safety video, excellent in fact. Here in NZ we refer to the 3 part process as Prove, Test, Prove.
I can hear the screwdriver.
It's a sonic one
That's not a screwdriver! Wow.
me tooo buzzzz buzzzz
HI, if you cant set a multimeter on the correct setting for proving a circuit is dead than maybe you should leave the testing alone.
Well said.
Yes that is precisely what i was thinking!
Also prove the multimeter.
Maybe. I use multimeter and for all the rare cases I short circuit the wires so they abosutely are not live. I can't recommend it thou. Don't fall from the ladders when doing that.
def ender I have used one of those screwdrivers once or twice when desperate, but always checked it's working with the power on first. Still I don't trust them and have always used my multimeter. Never had a problem as I always Che know my settings before using. Kinda pilots check list mentality - leads in correct sockets - check, a/c range - set and again check it's working on live before checking to see its off.
thank you for explaining how the fluke work as an apprentice i have found this useful
John, pleased to see you discussed the use of a proving unit but it would have been helpful to mention that any test meter/indicators should be GS38 compliant - meaning that the test leads should be fused. I wonder who you aim your video's at because any qualified and suitably trained person would know how to use a Multimeter and know whether they had it on the correct setting or not.
Mr Ward, I’m very much enjoying your informational videos. They are the perfect companion to the City & Guilds courses.
I have a question for you regarding safe isolation. In your video here, and in the labs at the college they only ever show safe isolation of the complete system i.e. testing at the load side of the isolator to ensure all circuits in the consumer unit are dead. Are you able to show how you would isolate an individual circuit, for example the lighting circuit, whilst leaving the other circuits live?
After doing some DIY work over the years including 3 phase, one extra safety tip I do after checking the power is definitely off, is touch the wire with the back of your fingers. That way, if the wires were still live and all the muscles in your arm and hand contract, your arm/fingers will be pulled away from the live wires, instead of gripping it harder if you had used the inside of you hand.
Depends what phase you touch🤣🤣
@@MegaMetinMetin Makes no difference. Your grip would still contract with any of the three phases.
@@matthewcummings9024or you could put your tongue on it!
@@jablot5054 Or worse! 😱🤣
don't do that.
50ma is all it takes to kill you.
But what if neutral wire is accidentaly disconnected or corroded away?? Two lead testers will not indicate voltage on live wire. Neon screwdriver is the only tester that will be able to indicate dangerous voltage in such case! It's the only one tester that really indicates if current will be going through your body if you touch the wire. It's quite reliable if you test it before and after use and if you learn to watch the lamp carefuly. However if the small resistor inside gets shorted, you will get nasty shock.
Can I just add you need to test not just L-N but L-E and N-E as a faulty switch or RCD may break the circuit N but leave the L connected. Also 264v is above the maximum supply voltage you should be getting ESQCR specifies 230v +10% / -6% so 216v to 253v.
Brilliant straight talking and informative great stuff
There is a little flow in your presentation: let's pose for the moment that the neutral wire is broken. Will those fancy testers show that the power is on the live wire? What will happen if you 'reverse the polarity' and touch your Fluke main probe to the ground and the auxiliary probe to the live pin? Just curious.
Yes, they will show live even with only one terminal connected.
Reversed probes makes no difference.
Thank you. So you do not have to use both probes when testing? Just the main one will show live wire?
The one probe indication is a secondary feature, similar to those 'volt sticks' with the red LED in the end. Both probes should be used, and that is the only way to get a display of the actual voltage.
It is useful in that it shows instantly of a potential lack of live or Neutral but just as a neon screwdriver is not a trustworthy tool, the proper checks need to be made.
People still don't get it do they !
John I noticed that your Fluke was reading 263 volts. I have been left the UK now for 12 years but before I left the voltage was 240 volts.
Then the decision was made to make the UK the same as the EU continent at 230 volts. There was a tolerance though of I believe 6% so it allowed the UK to still operate at 240 because it was covered in range by that 6%.
But 263 is out of that range isn't it?
263 is far too high, the limit is 253 (+10%). The test setup in the video was supplied from an isolating transformer, which has a higher than normal output voltage with no load connected.
OK on that John. That explains the 263 volts shown on the Fluke.
John Ward I don't understand at times when you test neutral you can see that there is a current flowing through.
Great video, thank you for sharing your extensive knowledge.
I have an Di-Log DL114 auto ranging MM with a red light which is detects current on non contact basis or if one of the probes makes contact to a live conductor.
It has a built in torch too. £28
Watch carefully at 9:05 and you will see the Fluke tester does incorporate this.
Thanks for understand. I'm from Western Aussie. about Safety and RCD
John - could you do a video on DIN rail terminal blocks? I'm aware that there are types that 'bus' together and others that are electrically isolated. Thanks
Good video JW, I have a cheap multimeter here (a present someone got me, I would never buy cheap multimeters myself) thats going spare I can send you so you can blow it up when you do your video on CAT ratings. I have all fluke meters anyway so it wouldnt be a loss.
That's a really good Multimeter though. I have the 115 and typical of Fluke it's so robust. Easy to read display, easy to switch modes.
Those who didn't check first aren't saying anything any more!
1:23 - is that a sound effect added as an easter egg or are we getting 50hz buzz straight off the mains? 😆
It's interference from the mains, the microphone used at the time was rubbish.
. I used to have an issued with an old Jaguar car draining healthy battery after 24 hours - any tips to fault find this type of problem?
Very informative and thorough. Thanks
When testing at a socket for example. You should get 240v between live-neutral and live and earth. However should you get continuity between earth and neutral. And also when testing dead, should you get continuity between live and neutral, if appliances are still plugged in, but no continuity between earth and neutral?
In the Netherlands appliances for proving 'dead' mains have to comply with NEN-EN-IEC 61243-3 or equal ( According to NEN 3140: 2015 6.2.3.101 ). A multimeter is not produced according to this standard and is therefor not suitable to use it that way.
The procedure for proving 'dead mains ( 3 fase and neutral and PE )is as follows:
-Be sure the tester works
-test L1-PE , L2-PE,L3-PE,N-PE L1-N, L2-N,L3-N, L1--L2 ,L1-L3 ,L2-L3
and finally the last test for assuring the tester is still in working order.
for a 230V it would go as follows
-Be sure the tester works
test L-PE, N-PE,L-N
and finally the last test for assuring the tester is still in working order.
I wonder if there are different sets of rules for proving dead mains between countries?
JW....I have a question about the Drummonds,
When I was an apprentice, they told me "To prove him dead, you must cut off his head".
That was some time before I changed careers and got into the electrics.
GREAT VIDEOS JOHN
HAVE YOU EVER HAD A SHOCK IF SO HOW MANY AND WHAT SITUATIONS
Very informative and straightforward. Thanks.
So what interference was happening with that neon screwdriver?
I have a chinese version of the multifunction voltage tester (UNI-T UT15) and it has an on-time limit of 30 seconds followed by a rest period of 10 minutes, presumably due to power dissipation in the input part of the device that covers the wide range of 12V to 690V. I wonder if the Fluke voltage tester you showed also has that test period limitation?
+ridefast0 Fluke specification has on time 30 seconds, recovery 240 seconds (4 minutes).
Thanks - so it looks as if the heat is managed better in the Fluke. No surprises there.
...aaand even *AFTER* all that excellent advice, if your're going to work on two bare wires for a ceiling fixture, touch both conductors together with one hand BEFORE reaching with the other. If you have done what is aptly described here, it should be a simple final check before potentially sending a deadly current through your heart. Worst case scenario, you burn a hole in one hand instead, while you scratch your head with the other, wondering how the hell did that happen.
Hi.can you explain a 3phase and neutral supply how is there not 3 neutral supplies when there is 3 100 A fuses I thought if 50A goes along the phase cable 50 A comes back through the neutral which would put 150A through the 1 neutral overload it I am talking about using the 3 fuses for 240 v systems can you tell me how this works and does not overload the 1 neutral. Cheers
If only one phase is loaded, neutral current will be the same as that phase. If more than one phase is loaded the neutral current will be less, and if all 3 have the same load connected neutral current is zero.
The three phases are not the same, each is phase shifted by 120 degrees, so that when one is at the peak AC voltage, one of the others will be at zero. Current flows from one phase to another, and the neutral just handles any imbalance.
More extensive description here: en.wikipedia.org/wiki/Three-phase_electric_power
I was nearly killed once when I trusted a volt stick so I can confirm they are not suitable (I tested it on a known live wire and it lit up, tried it on one I thought I had disconnected - tried it several times) then cut the wire resulting in no more wire cutters !
Just wondering - if the RCD had developed a fault or was wired wrong and it was only switching the blue wire wouldn't the suggested technique in your video give a false safe indication?
No
I get concerned by the number of people saying, "i have had lots of shocks and feel fine", "or 240v or 110v doesn't hurt that much, stop being a wuss" what is all the fuss about?" ect, They completely miss the point, it only takes their body resistance to be low enough to cause a fatal shock, which is only milliamps, why do you think an rcd is designed to trip as low as 30ma? The mains supply in your house is more than enough to kill you, whether its 240v in the uk, or 110v in america, they are both enough to kill, your body resistance determines the shock level of it being a slight tickle or nip to meeting your maker (in other words DEAD!!!) Electrocuted! and of course as you say john we won't be hearing from them.
John am i wrong here - a/c v == 240 , you did a test for live & it showed 261 v , how thats ?
Thanks for the valued advice.
261 is too high for mains and would potentially cause an issue with a domestic boiler pcb. just a thought
I think he's using an isolating transformer, and running it under negligible load, so the voltage is higher than it would be on the actual mains.
That closing statement I believe has to with something called “Survivorship Bias”
Where you only look at the survivors and ignore failure
And then use that to be overly optimistic towards something
Or in this case: be overly lax towards safety
And when the supply is off- make sure it is under your control! About 45 years ago i was examining a long extension lead that had failed- A man walked past the plug and an reasoned that the reason for failure was that it was not plugged in- so he did that- he then ran outside to investigate the screaming..... I was me connected - the man was my brother........... I often wonder.
I do love your videos, your like a teacher :)
I'd say that, if you don't know how to set multimeter up, you definitely shouldn't even think about doing anything, anywhere close to mains!!!
and you would be wrong.
John, I tend not to use any of this equipment when I’m testing my circuits; instead I do prefer to get my little brother to touch the wire I’m unsure about. It’s simple if he doesn’t get a shock I know the circuit is dead, if he gets thrown across the room it means the circuit is live! Easy!
Hi John, Would you trust the LAP MS8922B AC/DC 2-POLE VOLTAGE TESTER from screwfix for 240v home use
I haven't used it, but it is made by a known test equipment manufacturer (Mastech), Screwfix have just had it relabelled for their own use. It's very basic but should be OK for voltage indication.
Your Video is done perfectly by the Book. Sadly the Book does not cover everything. it is also slow to adopt new stuff coming up which in my opinion makes much sense.
In no particular order:
1. You didnt mentoin that the most common tester can also detect/show dangerous Voltages with only one wire connected. you can briefly see it at 9:05 before you connect the N that the AC lamp briefly lights up alone. If this happens with both leads connected but its not showing a Voltage you should double and triple check because something is probably very wrong then.. (and the first tester you showed would very likely have shown something in that case) - yes such things happen. A Co-Worker once told me about such a situation where a Cable was cut inside a Wall with a Wall Chaser but only N and PE got cut, L was still connected - he was glad he had one of the Screwdriver type Tester at hand because the other testers he used before didnt show anything (this was probably 20 years ago so they were older ones without that feature)
2. You said tha the Test Leads must be insulated that at most 4mm of it is uninsulated. While i agree with the general thought in practice these kinds of probes are simply not useable because you cannot get the probe to contact properly in the most commonly used Connectors today (we use the Wago 221, and back when this video was made the previous generation which had the same problem), and it would be very wrong to assume that the wiring box is Voltage free if you cannot get proper contact with the wiring. I usually cut the Insulation a bit to mediate this - barely enough that i can click my Probe into a Connector of aforementoined Wago 221 (thats about 6 or 7mm exposed metal on the probe - this is also perfect for using the Test contacts on these Connectors.) The 4mm Rule certainly made sense back when these Screw Things were commonly used, but i am glad we screwed them..
3. While the Screwdriver-type Neon Testers are certainly not a good choice as Voltage Tester i like them for another purpose: they are perfect to unlock the Spring-type Terminals in Distributors, and also to Slide the N Disconnector. Or when you happen to come across a Screw Connector. Its pretty difficult to find appopriate Screwdrivers in the right Size as single Item (i dont need it included in a set of other Scredrivers, as usually only the small ones break). I personally would favour a Combination of a small Screwdriver and a Test Lead (basically a Screwdriver with a Ø4mm Socket for the test lead), but so far i had no success finding one..
As additional Measure: if you work with many Circuits and the way from the Distributor to the Working site is pretty long: there are also these new Fuse Finders which add an additional check. Plug them in on the desired Circuit, check for their Signal in the Distributor, Switch off Circuit and the Signal should disappear almost instantly (if it doesnt something is wrong). After that check again with one of the allowed Testers of course. When switching on do it the other way: plug in Transmitter on the Circuit you want to switch on, hold Receiver close to the Fuse and when switching it on you should quickly get a Signal. If not something is wrong and you should quickly switch the fuse off again and re-check your stuff. Certainy not a Requirement, but if you work with many Circuits it makes much sense in my opinion (better than leaving an unknown cable live while you go to check the Socket or whatever you are working on and walk back to switch it off if it doesnt check out).
I heard the Fluke proving units and others are not suited for use in domestic properties due to EMC. Is this true?
Hello John!
I like electricity, especially transformers, 3 phase motors, but also I like to work with circuits.
My question is : What type of multimeter can you recommand me?
I am looking for a Fluke T-130, but I also like Fluke 113 and 114.
Now I have a PeakTech 3340 which is working ok.
When using voltage probe testers, does it matter which terminal you put the needle in. If so, what terminals does the positive and negative go into? What would happen if you did it the wrong way? And also if I wanted to test a socket through the pins, where would I put the needles?
AC doesn't have positive or negative, and it doesn't matter which way round the probes are connected.
@@jwflame oh I see thank you
@@jwflame but you have live and neutral. 🙄 Polarity.
You can hear those probes when they make contact, must give out quite a pulse.
When you use that neon test driver, is it interfering with your microphone where you become part of the circuit? every time you touch it to the circuit, I can hear a faint buzz.
Self proving voltage and continuity testers, are they any good. Or is it best to get two separate units
A proving unit is still required, as it's necessary to create the 400+ volts to prove it with.
Some have a built in function to test, but that's only for confirming the indicators on the device are working, that can't replace testing it on an actual 400+ volt supply.
Well explained video. Thanks John.
Hi can you do a video on the sequence of tests r1 +r2 an loop impedance an the likes and why the tests are carried out thanks john
Roy Kirkham Yes, these are planned.
Do you want to sell your vase? if so, how much thanks
Which brand is the best or most popular for testing equipment?
Hi John may I check with you still able to find the test bulb with the screwdriver set (able to trip) ? As you show on the video 5.58 thank you.
That one isn't made now, the nearest equivalent is this: martindale-electric.co.uk/drummond-mtl10-test-lamp-p-1715.html
Hi John I think this one not able to trip the RCD ......... : (
Some of the Fluke testers like the T110/T130/T150 have the ability to trip the RCD , they have a switchable load function which will draw 30mA.
Get a Fluke; they are the dogs dangly bits
This info would be handy for working on automobiles, I think.
Also, a topic suggestion for a future video. Why does the US (where I live) only use 120 volts when apparently everywhere else uses 240 volts? I do hope you eventually cover something like this. Would be interesting to see.
+Bryan Young That's quite interesting. A mate told me his take on it, and that is, Americans were first to receive electricity and it came in the form of 110 volts. Since then other countries had got it and realised that the 230 - 240 volt system was a heap better (more power I suppose) however Americans already had the 110 volt too well established into their infrastructure that it wouldn't be viable changing! A theory that would need proven, however, no doubt interesting all the same!
From what I understand, we have 240 pumped into our houses, though it gets chopped into 120 somewhere along the lines. Like our stoves, washers and dryers all use 240, of course with a different plug so you can't screw it up and plug in a nightlight there.
+Bryan Young You are getting 220V/60 Hz phase to phase with a neutral in the middle providing two 110V/60Hz circuits (two phase 180 degree system). Most of the world gets 3 phases with 380V/50Hz phase to phase and a neutral at the star point providing 3 x 220V/50 Hz circuits. Britain and its colonies used to get 415V/50Hz and 3x240V/50Hz. So before brexit, the EU compromise was to label it all as 400V/50Hz and 3x230V/50Hz. Not sure if that will be rolled back after Brexit.
Hi JW Can you please explain what happens at the pole transformer at the centre tap. I have ideas but need professional help with this one. I am a 69 years old student of the "Works of Nikola Tesla". .... Regards ..... DC
That's quite interesting! Thank you for explaining so much. I'm curious why the sound jumps sometimes when you touch the wire with the probing rods. Can you explain what's happening? This is not meant as a criticism I really want to know what's causing this, because I want to learn more about keeping audio clean my own work. It just seems weird to me that doing this can affect the sound of your camera because there should be no connection between the things, right?
Michael Hübner It will be capacitive / inductive effects, mostly being coupled into the wire for the microphone.
Constant interference will be capacitive, and when connecting/disconnecting the probes inductive, as a small spark will be created at the probes - a similar effect when turning a switch on and off.
Watching again in 2024. I now own one of those Fluke voltage testers.
Hi John totally agree those screw drivers should be banned from sale
Your mains voltage is awfully high at 261! I think that's outside the +/- 10% of 230 by a LONG way!
Real story - I was working in Hong Kong once and while wondering the streets taking in the sites came across a street stall which among other things was selling a fairly respectable looking neon screw drivers. I also noticed it had "made in West Germany" stamped on it. Oddly I could also see inside the open door of the factory and the people making the neon screwdriver. Perhaps there is a section of Kowloon known as West Germany.
That was around 20 years ago but perhaps only the location has changed today.
***** HE is likely on an unloaded isolation transformer or varac, so the extra voltage is expected.
KingOfKYA Yes, it's an isolation transformer. Otherwise it would not be possible to trip the RCD on the test stand without also tripping the rest of the circuit.
***** Ah right that true or you wold be poping the main rcd breaker. Another potentially interesting topic would be safety procedures when you have to work on live circuits, and possibly thouse with multiple power feeds.( datacenters hospitals etc)
hi john,
what do you think of the various test leads that have a self test (working ) function built in ? ( ie. push a button th check if function is ok )
I have one issue with two test prong units. In case of faulty neutral connection most of test units don't notify about potential of getting shocked. My coleg once got pretty nasty shock testing with a multimeter( somebody has pulled the neutral wire from the junction box).I always test with cheap screwdriver type indicator. And its easier to carry it around than a two prong unit. I never had faulty indicator but i still test it on known live circuit before i use it to diagnose something. It has it's fault with the fact that it is hard to see the light shining in lit condition especially in daylight. Most indicators brake quite easily especially if you use thame as a screwdriver. And I believe there are conditions that it could not light up on live circuit (like on DC) but I didnt enquterd it yet in my work.
P.S. In case of faulty neutral it quite easy to test it just by connecting some load on circuit and checking if indicator lights up on neutral terminal.
Watch carefully at 9:05 and you will see the Fluke tester does incorporate this.
superb , brief and clear thank you son
Actually fluke 117 has a great feature for proving dead, which is the auto low impedance volts range, definitely one of my favourite multimeters out there
Great, however you are missing the point of the video.
Very useful. I will treat myself to a proper tester.
Hi,
I am a trained 'Authorised person' and would like to point out an error in the proving for dead procedure described above (around 11:00 onwards).
The correct procedure for proving dead is a five stage (not three stage) procedure:
Step 1 - Prove your tester (check it is working)
Step 2 - Test Phase to Neutral (repeat for all three phases in a three phase installation)
Step 3 - Test Phase to Earth (again repeat for all phases)
Step 4 - Test Neutral to Earth.
Step 5 - Prove your tested again (Check it is still working).
Without steps 3 and 4, the neutral or even earth could be live and you would not be aware as the neutral and live are at the same potential (i.e. both at 240v or both dead, but with a live earth).
Also, for the electricians using mulitmeters to prove dead (I used to do this myself!), I would like to point out that the real danger with this is the possibility of the 'multi' meter accidentally being in current measuring mode. (Anyone who says they have never tried to measure volts in current mode is either superhuman or lying). In most cases, this will just lead to a blown fuse and some embarrassment. In the worst case, you might believe the circuit is dead (though steps 1 and 5 above should contradict this) or worse, draw an arc with a risk of flashover and burns (it has happened).
Work safely folks.
Gavin Minion just get a basic multimeter that's always set to volts to check voltage
I MUST SAY I HAVE NEVER HAD ANY TROUBLE WHILE USING MY DURITE 0-798-50 CAT 2
TESTED IT AGAINST MY OLD AVO7 RESULTS OF WHICH ARE VERY VERY CLOSE
I GET ON VERY WELL WITH EITHER OF THEM
I love John's videos, but this one I find lacking. For example, in case of neutral which gets to live potential (non that rare, due to shared neutral issues for example - and that can happen even in the middle of the work, not just at start!), in this video *ONLY* the Fluke (not main LEDs, but aux LED at top right) and "dreaded neon screwdriver" will actually work safely without endangering your life! Over here proper procedure for preparation of work on electrical installation was:
(1) on the live output of main switch (input limiter/main breaker/main RCD) and neutral, check the instrument is working properly and input neutral is not broken (like main LED on Fluke or voltmeter or lamp test in this video) .
(2) Turn off the breaker and check that neither the live nor neutral are at above-ground potential (NOT just the lamp/multimetar test, which wouldn't show broken neutral or neutral at 220V! Only Fluke aux AC LED shown at 8:43 and neon screwdriver from this video work for this!)
(3) check on the input of main switch instrument is still working.
(4) doublecheck with instrument that output of main breaker is really off.
(5) short-circuit output of (now turned off) main switch live and neutral with your marked patch wire which you were carrying always with instruments/tools.
(6) post a notice of "hazardous environment, warning not to touch the breakers, date and time of start of work and contact phone number" over the panel with patch wire and main switch.
(7) proceed to work on the installation.
This had a number of *additional* safety advantages to methods presented here, including: deterring people who wanted power and went to turn breaker back on while work was in progress (6), covering broken neutral (1), covering neutral at live potential (2), doublechecking (as just one check may not have made contact correctly) there is no live after input (2,4), making sure that even if live were to be introduced in any way while work is in progress, it would case dead-short and disconnect upstream instead of risking life of personnel (5).
Of course there were also reverse procedure before turning power on (most importantly undoing 5, checking it is undone, and checking live/neutral before turning back on)
what happens if you put the probes the wrong way around?
so in the video you were putting the black com cable probe onto the neutral & the red on live to get 261, but what if you did not know which cable was which or a cowboy job meant that you actually put the black com onto live & the red onto neutral...
what would happen then?
It's AC. You would still get the same voltage reading.
I dont really understand all the hating on the regular multimeter :/
"If you dont know how to set this up, it wont read correctly"
I'd say that if you dont know how to set up a multimeter, you'll need to learn how to, and not fall back to a possibly dead lamp.
The test before on a known live circuit would expose the dead lamp.
In Germany it's mandatory to test your voltage tester on a functional circuit before using it. And I prefer the 2-pole voltage testers with a neon indicator in one handle and a plunger coil instrument in the other one. The neon indicator is for high impedance testing, and if you press a button you can switch over to low impedance testing. The plunger coil is indicating the voltage. Needs no batteries, and the lifetime of the neon indicator is much higher as the one of a standard lamp.
But you won't get neon indicators showing the polarity on a DC-voltage anymore. Now they're using LEDs instead:
abload.de/img/img_0123gesjq.jpg
The problem is that if you use multimeter for this application, one day you will be in the hurry, or simply be distracted, or meter will be malfunctioning, and you will put it in wrong settings or something or read incorrectly. It is not a matter of if, but when.
Yup, something like the "HOLD"-function.
And multimeters have a high internal resistance. That's good for measuring inside of electronics, but not in a mains voltage circuit (reactive voltage). And the next thing is, with a multimeter you must turn away your view from the measuring point. And if working on a ladder a multimeter is very uncomfortable to work with.
Test on known circuit also proves the multimeter is set right, so multimeter is just as good in theory.
Nice vid JW although I didn't catch any reference to GS38 aside from the probe covers (with no mention of GS38) but I'll behappily corrected?